Indoor air pollution
and lower respiratory tract
infections in children
Indoor air pollution
and lower respiratory tract
infections in children
Report of a symposium and a workshop
held at the International Society of Environmental
Epidemiology, Paris, 4 September 2006, presenting
preliminary results of a randomized intervention trial in
Guatemala and discussing the implication for
policy, advocacy and future research
Executive summary
WHO Library Cataloguing-in-Publication Data
Indoor air pollution and lower respiratory tract infections in children: report of
a symposium held at the International Society of Environmental Epidemiology,
Paris, 4 September 2006, presenting preliminary results of a randomized
intervention trial in Guatemala and a workshop discussing the implication for
policy, advocacy and future research.
1.Air pollution, indoor. 2.Respiratory tract infections. 3.Randomized controlled
trials. 4.Health surveys. 5.Intervention studies. 6.Child. 7.Guatemala. I.World
Health Organization. II.Title.
ISBN 978 92 4 159572 8
(NLM classification: WA 754)
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Contents
Executive summary 1
1Introduction
2
2Summary of the abstracts presenting the main findings from the Guatemala Randomized Intervention (RESPIRE) study
Background of the study and description of the site
Objectives of the trial
Study intervention and effect on air pollution
Case finding and effect of chimney stoves on childhood pneumonia
Conclusion of presentations at the symposium
3
3
3
4
4
5
3Research lessons and future directions from the RESPIRE study
Trial findings not reported at the symposium Blood pressure Upper respiratory infections
Self-perceived health
Non-health outcomes
Other similar studies and sources for information
Methodological lessons and problems
Gaps in knowledge, research needs
Additional efficacy trials
Effectiveness trials
Cohort studies
Case-control studies Advanced methods to be considered
Additional Guatemala studies (in addition to ongoing CRECER study)
Policy and advocacy implications 6
6
6
6
7
7
7
7
9
9
9
10
10
10
11
11
4 What do we tell governments and donors?
12
5References
14
6 Participants
15
Contents
iii
Acknowledgement
WHO wishes to thank Dr Nigel Bruce, Division of Public Health, University of Liverpool, Liverpool, UK, Dr Byron Arana, Universidad del Valle, Guatemala and Dr
Kirk Smith, University of California School of Public Health, Berkeley, CA, USA for
convening the symposium “RESPIRE – the Guatemala Randomized Intervention Trial”
at the International Society for Environmental Epidemiology (ISEE), Annual Meeting,
Paris, 4 September 2006; and for the presenters at the symposium for contributing their
presentations. It also wishes to thank the participants in the subsequent workshop for
their contributions and opinions, and Dr Harry Campbell, Public Health Sciences,
University of Edinburgh, for chairing this workshop.
iv
Indoor air pollution from solid fuels and risk of low birth weight and stillbirth
The workshop was supported by the Department of Child and Adolescent Health and
Development, WHO, Geneva, Switzerland, with funds made available through the
U.S. Agency for International Development (USAID).
Executive summary
To study the effect of the reduction in air pollution exposures on health outcomes such
as pneumonia in young children, a randomized control trial (RCT) using improved
woodstoves with chimneys as the intervention was carried out from 2002–2004. The
study aimed at improving our understanding of the relationship between pneumonia
and indoor air pollution. It was undertaken in the highlands of Guatemala on a population of over 500 Mayan Indian children aged 0–18 months in households that used
open wood fires for cooking.
At a symposium at the International Society of Environmental Epidemiology in Paris in
September 2006, preliminary results of the trial were presented as 5 papers, – describing the process and methods in conducting the control trial of acute lower respiratory
infections and indoor air pollution; – evaluating the performance to optimize casefinding for childhood pneumonia; – examining the impact of a chimney wood stove on
the risk of pneumonia in children aged less than 18 months in a rural area; – assessing
the impact of a chimney stove on women’s lung health in a rural wood-burning community; and – measuring the impact of social and environmental factors on a vulnerable population by their effects on birth weight, growth, and mortality.
This symposium was followed by a workshop which summarized first some trial findings which were not reported at the symposium, such as effects on blood pressure, upper
respiratory tract infections, self perceived health and non-health outcomes (e.g. time
and fuel savings). Workshop participants discussed methodological lessons learned and
problems encountered, and gaps in knowledge and further research needs.
It was concluded that further trials in different geographical settings are needed.
Designs, potential sites and request for such research were considered. Nevertheless, it
was considered that there was now a more solid basis for arguing about the effect of air
pollution reduction on child health, and that advocacy efforts to donors and governments needed to be scaled up, to address this major risk factor for child mortality.
Executive summary
1 Introduction
Indoor air pollution and lower respiratory tract infections in children
The deaths every year of nearly 2 million children under the age of 5 years in developing
countries from acute lower respiratory infections (ALRI) have not been fully accounted
for by well-established risk factors such as malnutrition. Over a dozen observational
studies have found consistent associations with indoor air pollution (IAP), including
the use of solid fuels in households, but they fall short of fully confirming a causal
exposure-response relationship. A randomized control trial (RCT) using improved
woodstoves with chimneys as the intervention, originally planned in the mid-1980s
but not funded until 2001, was recently carried out to improve our understanding of
the relationship between ALRI and IAP. This study, known by the acronym RESPIRE
(Randomized Exposure Study of Pollution Indoors and Respiratory Effects), took place
from 2002 to 2004 in the highlands of Guatemala on a population of over 500 Mayan
Indian children aged 0–18 months in households that used open wood fires for cooking.
Primary funding for the trial was provided by the U.S. National Institutes of Health,
with additional contribution by WHO.
2
Summary of the abstracts
presenting the main findings
from the Guatemala Randomized
Intervention Trial
Five presentations at the symposium on the randomized intervention trial in Guatemala were concerned with:
– describing the process and methods in conducting the control trial of acute lower
respiratory infections and indoor air pollution;
– evaluating the performance of methods used to optimize case-finding for childhood
pneumonia;
– examining the impact of a chimney wood stove on the risk of pneumonia in children
aged less than 18 months;
– assessing the impact of a chimney stove on women’s lung health;
– measuring the impact of social and environmental factors on a vulnerable population
by their effects on birth weight, growth, and mortality.
Another symposium presented the findings on biomass smoke exposure among the
Guatemalan infants who participated in the trial.
The abstracts are accessible at http://ehs.sph.berkeley.edu/krsmith/page.asp?id=19
Background of the study and description of the site
In 1991 an international committee was established by WHO to locate a suitable site
for a randomized control trial based on criteria such as local health situation and logistics, exposure to indoor air pollution (IAP), and institutional conditions. A dozen sites
in Asia, Africa, and Latin America were examined, and Guatemala was chosen. Pilot
studies were undertaken in the 1990s before launching the trial in 2001.
Objectives of the trial
The main aim of the randomized trial was to determine the impact of using improved
wood stoves with chimneys (the intervention group) on ALRI incidence in children
aged <18 months, compared with the use of traditional open fires (the control group).
2. Summary of the abstracts
The population in the selected site are indigenous, primarily agricultural, Mayans living
at an altitude of 2200–3000 m in the western highlands of Guatemala. Their local language is Mam, with Spanish as a second language. Nearly all households in the area use
only wood for their fuel requirements. Pre-intervention ALRI rates in young children
were estimated at 0.5/child-year.
Other objectives were to quantify the difference between the two groups in the children’s exposure to indoor air pollution in relation to the risk of ALRI, and to describe
the relationship between exposure reduction and health outcomes for the mother and
child (e.g. birth weight, growth and mortality among the infants, and respiratory health
and lung function among the mothers).
Study intervention and effect on air pollution
Some 5500 households in the study area were screened for possible recruitment based
on the following: use of an open fire for cooking, presence of a pregnant woman or child
under 4 months, willingness to participate, and statistical criteria. From a total of 534
households recruited, 518 (97%) contributed to the final dataset. After baseline household and indoor air quality (IAQ) surveys, the households were randomly assigned
to receive an improved chimney stove (plancha) at the start of the study (intervention
group), or at the end of the study when the child reached the age of 18 months – having
been the control group during the trial – or when a household dropped out. The plancha
was popular and capable of substantially improving the air quality in the kitchen; if any
structural problems appeared in the plancha, it was repaired during the study.
Indoor air pollution and lower respiratory tract infections in children
Personal 48-h carbon monoxide (CO) exposures were obtained every 3 months for
all the study children and every 6 months for mothers. Intensive monitoring of CO
and particulate matter (PM) was conducted in a 13% sub-sample, along with outdoor
monitoring and assessment of exposures from use of wood-fired saunas (temascals).
At baseline before intervention, the control and intervention groups had similar child
CO distributions (mean values 2.4±2.4 ppm and 2.5±1.8 ppm), respectively. In the
control group, there was a small reduction to 2.0±2.2 ppm during the trial, which may
be attributed to changing time-location patterns associated with age. However, a much
more dramatic reduction in exposure to 1.0±2.3 ppm was observed in the intervention
group. Adjusting for gender, age, season, and weekday, the mixed model estimated a
44% reduction (95%CI: -48 to -39%) in child CO associated with the improved stove
intervention. Younger age, female sex, and the rainy season were associated with slightly
higher exposures. The intraclass correlation coefficient (ICC) was 0.28, indicating the
limited reliability of a single measure as a surrogate for long-term exposure.
The plancha stove provided large reductions in child CO exposure. The low ICC indicates that most of the variability among the data is within-subject rather than betweensubject. We will examine this issue in light of the repeated measures on each child and
the observed predictors of exposure and consider the implications for child-specific predictions using the BLUP (best linear unbiased predictor) and attenuation of the hazard
ratio for the effect of biomass smoke exposure on infant ALRI.
Case finding and effect of chimney stoves on childhood pneumonia
After stove installation, case finding was carried out through weekly home visits by
fieldworkers (FWs) trained to apply IMCI methods to recognize key signs of ALRI
(fast breathing, chest wall indrawing, etc.). Cases were referred to a physician (MD)
in the community centre; all referrals had their arterial blood oxygen saturation measured by pulse oximetry (SpO2). A RSV (respiratory syncytial virus) direct antigen test
was performed on cases diagnosed as ALRI, and chest X-rays were read blind by two
radiologists and validated by a WHO panel. Anthropometry was conducted regularly
and birth weights were recorded within 48 hours of delivery. Verbal autopsies were
conducted on all child deaths.
The outcomes ranged from very sensitive but non-specific (assessed by a field worker),
through moderately specific (diagnosed by a physician), to highly specific – defined
according to criteria of a positive RSV, hypoxia measured by pulse oximetry, and chest
X-ray (for pneumonia).
Fieldworkers referred >90% of children who met the ALRI criteria, but only about 75%
of them were seen by a physician. However, successful referral by the intervention plancha group was about 7% higher (significant for some outcome definitions), a trend also
seen in compliance with RSV testing and X-ray referral. Consistency between study
physicians in recognizing the respiratory signs used for diagnosing ALRI was adequate,
with no clear evidence of bias. There was good consistency between clinical diagnosis/severity and oxygen saturation, with substantial differences in mean SpO2 between
children with physician-diagnosed ALRI and acute upper respiratory infections (AURI)
(p<0.0005). Chest X-rays were not available in 20% of cases due to parental mistrust of
hospital facilities and transportation difficulties. Parental acceptance of hospital referrals increased over time from 70% in the first 6 months to 95% in the second year.
Based on the preliminary analysis presented at the symposium, fieldworkers (FW)
identified 735 cases with ALRI signs after 597.6 child-years of follow-up (incidence of
1.23/child/year). There were 265 cases of physician-diagnosed ALRI (incidence 0.44
episodes/child/year). Preliminary intention-to-treat analysis found rate ratio for intervention vs. control of 0.84 (95% CI: 0.73,0.97; p=0.02) for all weeks with FW-defined
ALRI; 0.85 (95% CI: 0.67,1.08) for physician-diagnosed ALRI. There was almost 40%
reduction between groups over time for RSV-negative cases with hypoxia (SpO2 <87%:
> 2SD below mean for well children at study altitude), with an OR of 0.62 (95% CI:
0.36,1.05; p=0.07), a potentially important finding since these cases are (a) likely to be
bacterial and (b) have more severe disease, and hence the highest mortality. In contrast
there was no impact on hypoxic RSV-positive cases (OR: 1.01 95%CI: 0.60,1.73). The
overall child exposure reduction based on modelling of 48-hour CO measurements was
about 44%.1
The sample sizes were not expected to provide sufficient power for statistical significance
in birth weight and mortality, but the RESPIRE study offered a unique opportunity
to monitor the health of children in one of the poorest regions in Guatemala. Intensive
surveillance during the study increased the ability to detect low birth weight (LBW),
disease incidence, and death and thus may provide more accurate data about this population than national statistics. This population is under high stress as measured by all
indicators. Despite active weekly health surveillance and two full-time physicians, 23
deaths occurred, indicating the high vulnerability of these children to common, treatable illnesses, which can proceed from first symptoms to death in a few days.
There were consistent reductions in ALRI between the intervention group (using planchas with chimney) and the control group (using open wood fires), as determined by
fieldworkers and physicians. If confirmed, the observed 40% reduction in severe RSVnegative cases strongly supports the case for giving high priority to measures to control
indoor air pollution.
Conclusion of presentations at the symposium
The odd ratios and Cl presented are based on the preliminary analysis at the time of the Symposium,
and might change slightly with the definitive analysis.
1
2. Summary of the abstracts
The Guatemala randomized intervention trial, 2002–2004, confirms the benefits of
reduction of indoor air pollution by the use of plancha stoves with chimneys for household cooking. In particular, the benefits include a lower incidence of acute lower respiratory infections among infants up to the age of 18 months.
3 Research lessons and
future directions from the
RESPIRE study
Reported here are the topics discussed at a Workshop following the Symposium in Paris
on 4 September 2006 on indoor air pollution (IAP) and acute lower respiratory infections (ALRI) from the Guatemala Randomized Intervention Trial (RESPIRE), which
brought together about 20 people including investigators and other participants from
the meeting.
Trial findings not reported at the symposium
Indoor air pollution and lower respiratory tract infections in children
Blood pressure
Both diastolic and systolic blood pressures dropped about 3.5 mmHg in the plancha
intervention group and again in the control group after echo intervention, an effect
stronger than that achieved by salt reduction in most studies. This finding is the first
outcome analysed in the sub-study examining the effect of the intervention on indicators of heart disease risk in a subsample of mothers aged ≥38 years and grandmothers
of the children in the main study. A paper has been submitted for publication with
these results; the variability in heart rate, which was measured using Holter monitors,
is now being evaluated. Similar findings have been found in some, but not all, studies
of outdoor air pollution.
The development of heart disease is of major international interest; its importance locally will depend on the background rate, which is determined by a number of risk factors
including diet. As blood pressure (BP) is relatively easy to measure and interpret, it is
recommended that monitoring of BP be included in future studies, both observational
and experimental. Case-control studies are probably needed to elucidate the impact on
active heart disease.
Upper respiratory infections
The usefulness of acute upper respiratory infection (AURI) as an outcome measure was
questioned and discussed. It is unlikely that they will be meaningful outcomes in any
trial as they are too frequent in a childhood population. It may be that chronic bronchitis cannot be disentangled in the current trial because cough is an entry criterion
for assessment. Clearly this is not a significant aspect of the global burden of disease
(GBD), but it may be very important to mothers and hence important in promoting the
use of improved stoves.
Self-perceived health
Based on a self-perceived health questionnaire, most women felt that their health had
improved with use of the plancha stove, but only half felt that it had improved their
children’s health. A reduction in sore eyes was most frequently mentioned along with
improved cooking position, shorter cooking time, and less worry about child burns.
The most common complaint about the plancha was a longer time needed for cutting
wood. Only a small number indicated that it was colder in the kitchen. The reported
symptomatic benefits are consistent with analysis of the longitudinal data for the full
study sample, which showed that the prevalence of sore eyes and headache over an 18month period was significantly reduced in the plancha group (Díaz E, Smith-Sivertsen
T, Pope D, Lie RT, Díaz A, McCracken J, Arana B, Smith KR & Bruce N. Eye discomfort, headache and back pain among Mayan Guatemalan women taking part in a
randomised stove intervention. Journal of Epidemiology and Community Health, 2006,
in press).
Non-health outcomes
Time was saved during cooking and in collecting firewood. Saving of fuel was not an
outcome in Guatemala because the planchas used were not significantly more fuelefficient, at least by measurement. However, it was noted that the women seemed to
think they saved fuel, which may indicate that current measurement techniques are
inadequate.
While stove developers have produced more efficient stoves, their acceptability is always
a problem. The Guatemala plancha may not be ideal for fuel consumption, but it was
acceptable and used locally. See http://ehs.sph.berkeley.edu/uat/publications/Maxwell/
Granderson-05-1.pdf
As noted in the surveys, the benefits of the plancha type stove include a reduced risk of
childhood burns, improved kitchen hygiene, and enhanced ergonomics of cooking due
to raising the working surface from the floor and enclosing the fire.
Other similar studies and sources for information
The findings of the RESPIRE trial will be useful in informing the ongoing analysis
of World Health Survey data to investigate links between respiratory symptoms in
under-5-year-olds (i.e. cough, rapid breathing) and the use of solid fuels for cooking
and heating.
Methodological lessons and problems
Pulse oximetry, which is easy and cheap to conduct and appeared to work well as an
indicator of severe pneumonia, could possibly replace assessment by a physician in larger
trials, combined with assessments by fieldworkers using IMCI. There are logistical and
ethical problems, however, because of the need to provide care if hypoxemia is found.
3. Research Lessons and Future Directions from the RESPIRE Study
A related trial is being carried out in Mexico by Isabelle Romieu. With monthly surveillance, however, most outcome assessments rely on the mothers’ recall over the previous
two weeks. A range of biomarkers, including those in blood, and women’s lung function are also being evaluated. Compared to Guatemala, much lower pneumonia rates
have been reported, possibly because of better nutritional status and enrolment of older
children up to 5 years of age. AURI assessment is still possible but as it is rarely fatal, its
importance as an outcome has been questioned .
Two major assumptions made in sample size calculations before the start of the randomized control trial (RCT) were generally validated:
• The background pneumonia rate, as represented by the rate found in the control
group, was nearly the same as that used in the calculations (0.49 instead of 0.5 per
child-year).
• The total “drop-out” rate from all causes after surveillance started – because of
migration, voluntary withdrawal, or missed weeks of surveillance (it is important to
set up a cut-off for consecutive missing weeks especially in communities with a high
rate of migration), or stopping before the child reached 18 months, or death – was a
little higher than that used in the calculations (23% vs. 20%).
• However, as there was also a significant loss (mainly due to death and miscarriage)
between the time of recruitment and the start of surveillance, future studies should
expand the number recruited beyond the lower limit indicated by calculations, as
was done in this study in which 534 children were recruited but only 518 entered
surveillance (97%).
A larger sample size would be important in future trials. This trial was borderline in
size (sample size was based on an outcome which is not 100% specific, so there was loss
of power; more specific outcomes yielded fewer outcome events; also, there was loss of
additional cases due to respiratory syncytial virus (RSV) stratification). Statistical significance was not reached for the main outcome measure (i.e. the number of physiciandiagnosed pneumonia cases), although the estimate was in the hypothesized direction.
The primary explanation is that one-third of cases were lost as RSV-positive. Assuming
a similar pattern of cases and drop-outs, the sample size at the start of surveillance
would have had to be about three times larger than the RESPIRE trial (>1500) to reach
significance at the OR of 0.86 that was found. A study of that size should give enough
power for low birthweight (LBW) also as an outcome.
Indoor air pollution and lower respiratory tract infections in children
Future studies should always measure RSV status in both pilot and main studies. Sample sizes can then account for the possibility that little or no effect will be observed in
RSV-positive children.
Site selection and exposure assessment protocols in future stove intervention studies
should carefully take account of the sources of exposure to combustion pollutants other
than the stove. In this trial, two major sources of exposure were not included in the
original protocols, which were modified as soon as their importance was realized. These
sources – the dieta (lying-in of mothers and babies next to an open wood-fire for 25
days after delivery) and the temascal (a traditional wood-fired sauna with high levels
of air pollution) – did not seem to be appreciably affected by the intervention, but
lessened the relative exposure reduction achieved by the intervention. Combustion for
cooking of animal food in this area seemed to be less important. Pilot work is needed
to determine the importance of these sources and to determine the optimal monitoring
techniques.
One of the advantages of this study site was that all significant combustion sources used
the same fuel, i.e. wood, making the interpretation of pollution monitoring data less
difficult. Future studies may wish to look for similar sites, which are common.
The methods developed for analysis of carbon monoxide (CO) in the breath and CO tube
measurement worked reasonably well in Guatemala and should be considered in future
studies. Evaluation is still underway, but current analysis indicates that temporal variation
(intra-household) is so high that up to ten 48-hour measurements per child would have
been needed to pin down individual exposures better than using group averages, instead
of the 4–7 measurements per child in the RCT. On the other hand, a few measure­ments
alone may be sufficient to obtain a reasonable estimate of the group average.
There is still a need for personal devices for measuring particulate matter (PM), small,
light, and quiet enough to be used in children. The CO–PM correlation, which allows
use of CO tubes, will not necessarily hold for mixtures of fuel types or fuel use patterns
in other populations.
Analysis of the time-activity sheets is pending, but will be complex and difficult to
validate. It should provide useful information for interpreting the exposure data. There
are no simple measuring methods that are well validated at this point, although much
work is now being done in the exposure field using small electronic devices, such as the
UCB Particle Monitor, and UCB Personal Locator developed during the RCT and now
being deployed in the second phase of studies at the site (acronym CRECER: Chronic
Respiratory Effects of Early Childhood Exposure to Respirable Particulate Matter).
If significantly large sales could be guaranteed, there would be an incentive to develop
devices designed specifically for these solid-fuel households by industry as has been the
case for vaccines, energy-conserving appliances, and other technologies. Specifications
for such devices would need to be worked out, however, with involvement of experts
familiar with health-damaging air pollution, engineering, chemistry, and field logistics.
Gaps in knowledge, research needs
Additional efficacy trials
As the Guatemala trial is one whose effects are at the border of significance, more efficacy trials are needed with pneumonia as an endpoint. A characteristic of this study site
was the high altitude and high levels of under-nutrition, but it is not known whether
and how these might modify the effects of reduced indoor air pollution (IAP) on pneumonia incidence. Given that policy is driven most effectively by locally derived evidence, it would probably be best to choose the next trial sites in Asia and Africa, rather
than a repeat in Latin America. The government of India has indicated that it would
fund local expenses for such a trial.
Whether, after these results, such a trial would be ethically acceptable was discussed at
the workshop. If not, it may be desirable to use an entirely different technology as the
intervention. Most likely candidates would seem to be the new generation of “gasifier”
stoves, which use biomass but burn nearly as cleanly as liquified petroleum gas (LPG)
and are coming into use in China, and biogas, which is widely used in several Asian
countries.
More research is urgently needed on low birth weight as well as pneumonia. A new trial
could start with randomization after delivery of a previous child. There is also little
quantitative evidence on how the use of different fuels and stoves is linked to the risk of
burns and scalds in children and adults, and on how such risks are affected by different
interventions.
Effectiveness trials
Given the large background of observational studies and the relative success in Guatemala, there is probably justification for identifying a location for a large-scale effectiveness trial. The fact that a randomized controlled effectiveness trial (or at least an
3. Research Lessons and Future Directions from the RESPIRE Study
Wherever the next trial is to be attempted, however, the experience in Guatemala indicates the extreme importance of good preparatory work to (i) find a suitable site in
terms of current pneumonia levels, biomass fuel use, and accessibility, (ii) carry out an
intervention that will not only reduce exposures but also be well accepted locally, and
(iii) find an excellent and experienced local collaborator.
individual household randomized study) could be very difficult was discussed, and other designs (including cluster randomized trials), quasi-experimental (comparison group
studies), and observational designs may have to be examined.
Electrification in South Africa might provide such an opportunity using a very clean
cooking source. The Shell Foundation’s and GTZ’s rollout of improved stoves and other
such large-scale plans like promotions of natural gas in Eastern Europe or of LPG
through UNDP and/or WLPGA (World Liquid Petroleum Gas Association) projects
potentially offer other opportunities, as would the existing national programmes for
clean fuels and biogas in Nepal.
Cohort studies
Although the children in the RESPIRE trial have been turned into a longitudinal
cohort (CRECER), with some additional sample enhancement, in order to look for
chronic effects including asthma, there is likely to be need for additional efforts along
these lines.
Of considerable advantage would be a multi-centre collection of birth cohorts that could
be followed for some years to examine a range of endpoints, including, for example, low
birthweight, premature birth, stillbirth, neonatal and post-neonatal deaths (depending
on sample size), early growth, etc. Such an effort has been proposed as part of UCB’s
extension of its Fogarty Grant in India in one site, Chennai.
A study approach, like the Tucson respiratory study (Martinez) for developing countries
which followed a cohort of children from birth and performed lung function measurements early in life, would be desirable in several sites and give invaluable information
on mechanisms.
Case-control studies
10
Indoor air pollution and lower respiratory tract infections in children
Case-control studies are needed for a range of endpoints that are suspected, but not well
understood, such as:
• Heart disease
• Lung and other cancers
• Asthma
• Low birthweight and neonatal/infant death
• Case-fatality of respiratory disease (TB, ALRI, COPD, lung cancer, etc.)
• Although a 4-site multi-centre study is currently underway in South Asia, there may
still be need for additional studies of TB, perhaps in conjunction with HIV status.
Advanced methods to be considered
To enhance their attractiveness in the frontiers of biomedical research and among
funders, future studies of any design should seriously consider such advanced methods
as:
• Sophisticated biomarkers of exposures, sub-clinical effects and disease, including
virology, macrophage viability, oxidative stress, etc.
• Genetic markers
• Interactions with HIV status.
Additional Guatemala studies (in addition to ongoing CRECER study)
• Obtaining birthweights from the RESPIRE/CRECER study area (for example,
Comitancillo where 85% of our study population came from) for a case-control
study.
• Evaluating cognitive development, which is being considered. (Standardized instruments exist from studies on the effect of lead exposure on cognitive development.)
• Rolling out the intervention in other households or other areas in Guatemala.
• Genetic testing – potential of a “mendelian randomization” type approach if appropriate genetic variants involved in causal pathways can be identified.
• Extension of follow-up of women using planchas and open fires (CRECER cohort)
to investigate differential rates of decline in lung function, and markers of airway
inflammation and remodelling (Janet Diaz, plan to submit for funding)
• Investigating the role of oxidative stress as a possible mechanism for PM increasing
the vulnerability to bacterial pneumonia (Plan to submit for funding).
Policy and advocacy implications
• Kirk R. Smith is involved in redoing comparative risk assessments of household solid
fuels in an effort funded by the Health Effects Institute, along with assessing other
environmental risks.
• Cost-effectiveness analysis (CEA) and cost-benefit analysis (CBA) have been conducted at global and regional levels; however, given the lack of epidemiological evidence,
the impact of improved stoves on childhood ALRI and adult chronic obstructive
pulmonary disease (COPD) was based on estimates. The CEA assumption of 75%
reduction in childhood ALRI looks far too optimistic in the light of the RESPIRE
findings; the CBA assumption of 35% reduction in childhood ALRI (a range of 10%
to 60% was tested in the sensitivity analysis) appears more realistic. To improve the
relevance of economic analyses to a specific decision-making context, CBA should
be repeated at national or sub-national levels in relation to specific, locally available
interventions.
• WHO is planning for expansion of the UNICEF/WHO advocacy paper on pneumonia published in September 2006. As UNICEF has a renewed focus on child
health, they have been contacted and are interested.
3. Research Lessons and Future Directions from the RESPIRE Study
• Some work will be done in the context of the Child Health Epidemiology Reference
Group (CHERG). The CHERG pneumonia group will undertake the task of estimating the distribution of etiologic agents and of estimating cause-specific trends,
splitting age-groups, and reviewing and estimating the impact of interventions.
11
4 What do we tell governments
and donors?
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Indoor air pollution and lower respiratory tract infections in children
We now have results to promote interventions, such as improved stoves, to reduce the
exposure to indoor air pollution, even though more research is needed. As a tool, a global mapping of possible interventions (e.g. stove types) and its acceptability by possible
users and donors would be useful. Good and acceptable solutions are better than perfect
ones which cannot be financed or are not locally accepted and sustainable. WHO and
the University of Liverpool (United Kingdom) are currently undertaking a review of
the impacts of past and ongoing projects/programmes to reduce indoor air pollution,
which might go some way towards a global mapping of interventions.
Because the cost of the historical next step up the energy ladder (i.e. kerosene and
LPG) has increased dramatically, there is now a widened “economic space” above the
traditional household use of biomass fuels. Even in those countries where the consumer
is insulated from high oil prices by government subsidies of these fuels, the governments are eager to find ways to reduce the enormous cost of the subsidy. This provides
opportunities for promoting processed biomass fuels and improved combustion devices
which cost substantially less than switching to petroleum-based fuels, but more than
many of the so-called improved stoves promoted to date. So-called gasifier stoves and
processed biomass fuels such as pellets, ethanol or plant oils are examples of ways to
achieve important reductions in actual emissions. These options are important because
the RESPIRE trial found that chimney stoves did not reduce women’s and children’s
exposures nearly as much as indoor pollution levels, probably mostly due to the exposures from outdoors or neighbouring dwellings that still cook in a traditional way.
These findings are confirmed by a number of other studies around the world and lend
strong support to the need to actually reduce emissions through cleaner combustion
devices rather than simply shifting the smoke outside.
There is a need to persuade industrial partners interested in investing in the development of new technologies to deliver affordable stoves with low emissions. To date, there
has been very low investment in this area relative to its importance, although there is
some activity now by Phillips, Bosch Siemens and a number of companies in China.
Increasingly, financing opportunities for programmes to promote interventions to
reduce indoor air pollution in developing countries are becoming available. The World
Bank, through its new investment framework on clean energy for development, has
placed some emphasis on access to cleaner fuels and technologies to reduce indoor air
pollution and associated health risks. The EU’s Energy Initiative is making available
198 million Euros for household energy provision (electricity and cooking energy) in
so-called ACP (Africa, Caribbean, Pacific) countries.
The availability of financing, however, needs to be complemented by increased awareness of governments as well as the lay public in developing and developed countries
about the health risks of indoor air pollution and the available solutions. Initiatives to
increase such awareness include the engagement of the health sector as well as schools
in promoting the message. The media – through radio/TV programmes and advertising, articles in science and women’s magazines and newspapers, as well as the internet
– play an essential role. Public visibility can also be increased by involving celebrities
and other champions.
4. What do we tell governments and donors
13
5 References
The following papers arising from the RESPIRE study have been published by the time
of printing of this report.
• Bruce N, Weber M, Arana B, Diaz A, Jenny A, Thompson L, McCracken J, Dherani
D, Juarez D, Ordonez S, Klein R, Smith KR, 2007, Pneumonia case-finding in the
Guatemala indoor air pollution trial (RESPIRE): standardizing methods for resourcepoor settings, Bull WHO, 85 (7): 535–544.
• McCracken JM, Smith KR, Mittleman M, Diaz A, Schwartz J, 2007, Chimney stove
intervention to reduce long-term woodsmoke exposure lowers blood pressure among
Guatemalan women, Environ Health Perspect. 115 (7): 996–1001.
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Indoor air pollution and lower respiratory tract infections in children
• Clark M, Paulson M, Smith KR, Canuz E, Simpson CD, 2007, Urinary methoxyphenol biomarkers and woodsmoke exposure: comparisons in rural Guatemala with
personal CO and kitchen CO, levoglucosan, and PM2.5. Environ. Sci & Tech. 41(10):
3481–3487.
• Díaz E, Smith-Sivertsen T, Pope D, Lie RT, Díaz A, McCracken J, Arana B, Smith
KR & Bruce N. 2007, Eye discomfort, headache and back pain among Mayan Guatemalan women taking part in a randomised stove intervention. J Epidemiology and
Community Health, 61:75–79.
• Smith KR, Bruce NG, Arana B, 2006, RESPIRE: the Guatemala Randomized
Intervention Trial (Symposium MS3 at the ISEE/ISEA Annual Conference, Paris),
Epidemiology 17(6) Suppl November, pp S44–46.
Electronic versions of these and further papers as they are published can be found on
the website http://ehs.sph.berkeley.edu/guat/page.asp?id=32
6 Participants
Harry Campbell (Chair)
Nigel Bruce
Maggie Clark
Mukesh Dherani
Anaite Diaz
Esperanza Diaz
Xaoli Duan
Rufus Edwards
Christine George
Dan Pope
Isabel Romieu
Kirk R. Smith
Michael Johnston
John McCracken
Sumi Mehta
Heidi Mestl
Luke Naeher
Lisa Thompson
Jim Zhang
WHO
Eva Rehfuess
Martin Weber
6. PArticipants
15
ISBN 978 92 4 159572 8